This invention relates to power saws and, more particularly, to hand-held power saws for cutting small trees.
Chain saws commonly are used for cutting trees. In the cutting of small trees, such as Christmas trees having a diameter of 3 to 5 inches, chain saws are difficult to use. Because of their bulk and weight, chain saws are awkward for an operator to use near ground level, especially for a long period of time. The danger of striking a rock or other hard object which might break the chain, leading to personal injury, is a real risk in using a chain saw along the ground. In addition, with chain saws it is difficult to maintain a consistent height above ground level over several cuts, and to make cuts parallel to the ground.
The ability to make repeated cuts at a consistent height, close to ground level and horizontal is particularly important in cutting Christmas trees. When the base of a Christmas tree is skewed from the horizontal plane, it must be trimmed again in order to mount it in a Christmas tree stand for household use. Also, as Christmas trees are harvested in large quantities at one time, it is desirable to have a way to cut them that is fast, relatively safe and easy to use.
Clearing saws are used for cutting weeds, grasses, small trees, and the like. A clearing saw generally includes a powerhead such as a small internal combustion engine for providing power, hand grips and a shoulder strap for holding the device in use, an elongate shaft for transmitting power from the powerhead and a clearing blade attached to a downwardly-directed hub at the end of the shaft. The shaft typically is several feet long, thereby allowing an operator to stand upright while cutting material close to ground level.
A clearing saw is very dangerous, particularly to the operator and bystanders, if its blade strikes the ground or rocks. Also, in conventional usage, cutting is only done along the lateral sides of the blade. This is because a clearing saw has a kickback zone along the front side, extending about 30.degree. in each direction from a centerline of the shaft. If the user tries to saw a tree in this zone, the rotation of the blade in one direction will kick the cutting saw laterally in the opposite direction. Commonly, a guard is provided to protect the operator. The guard is connected to the transmission housing that connects the hub to the power shaft. It leaves the blade exposed on both lateral sides for cutting.
It has been suggested that clearing saws could be used instead of chain saws for cutting Christmas trees. It is difficult, however, to use clearing saws for this purpose. When used in the usual manner, cutting along the lateral sides of the blades, it is hard to control the height and angle of the blade relative to the ground and tree trunk. When cutting Christmas trees, it is hard to see the saw below the branches. A clearing saw is also hard to control if the operator tries to cut straight forward. The operator can better see the blade in this position but kickback makes the saw difficult to control, leading to danger and inefficiency. As with chain saws, it is difficult to cut close to the ground with striking rocks with the blade, to cut uniform height stumps and to consistently cut the tree trunks horizontally.
It has been proposed to provide a guide shoe for spacing the clearing saw above ground level by connecting a U-shaped member to the transmission, behind the hub in the manner of the aforementioned guard, with an elongate leg extending forwardly beneath the blade and along its diameter. This approach is unsatisfactory, however, as the forward extending leg can bend upward against the blade and its position in front of the blade, intended to help guide the saw along a tree trunk, hinders sawing.
Accordingly, a need remains for an improved method and apparatus which allows an operator to easily and efficiently cut small trees near the ground, substantially parallel to the ground.